JPH0598198A - Coating composition and method for forming plural layer coating film - Google Patents

Abstract

PURPOSE:To obtain a coating composition containing a graphite flake pigment obtained by applying titanium dioxide to graphite flake particle surface subjected to oxidation treatment, suitable as a base coat consisting of 2 coat and 1 bake coating of car and capable of providing a dense coating film which is stable in light shinning feeling over a long period. CONSTITUTION:A coating composition containing a graphite flake pigment to which titanium dioxide was uniformly and densely applied is applied as a base coat to the graphite flake particle surface to which oxidation treatment by heating under oxygen-containing atmosphere and/or oxidation treatment by water soluble oxidizing agent was given and transparent top coat consisting of 2 coat and 1 bake is carried out thereon to form the objective plural layer coating film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating composition for coating steel sheets and other objects to be coated and a method for forming a multilayer coating film using the same.

[0002]

2. Description of the Related Art As a composition for coating an article to be coated (steel plate, etc.), a composition containing a color pigment and a thermosetting resin or a thermoplastic resin, which is generally known as a solid color paint, Further as a metallic pigment, for example,
Generally as a metallic color paint containing flake-like metallic powder such as mica flakes coated with aluminum, titanium oxide and / or iron oxide, copper, brass, mica-like iron oxide, bronze, stainless steel, titanium and chromium. There are known compositions.

As a method for coating an article to be coated with such a composition, the solid color coating or metallic color coating is applied to the article to be coated or directly on the cured or dried intermediate coating film surface, and the coating is cured. Or, a one-coat method of drying, and further, a clear coating material for forming a transparent coating film is applied thereon and then cured or dried again, or both coating materials are coated in the above order, and both coating films are simultaneously cured or There are known a two-coat method of drying and a three-coat method of coating a clear coating on the coating surface formed by the two-coat method and then curing or drying again.

Among these, the number of painting steps, the finished appearance,
In the solid color coating film, the one-coat method and the two-coat method in which the solid color coating material and the transparent clear are applied in the above-mentioned order and simultaneously cured or dried are often adopted in consideration of the coating film performance and the like.

On the other hand, in the metallic color coating film, a two-coat system in which the metallic color coating material and the transparent clear are coated in the above order and simultaneously cured or dried is often adopted.

The reflected light of a solid color coating film is a diffused light of a specific color that has been selectively absorbed by the color pigments contained in the coating film, and has no glittering brilliance. The light reflected by the film is mixed with the specific color light that has been selectively absorbed and returned from the color pigment contained in the coating film, and the light reflected by the metallic pigment. Because of the phenomenon of interference between these two lights,
The color of the metallic coating varies greatly depending on the amount of incident light and the angle of reflection, and the structure of the reflected light shows a variety of glitter.

A characteristic of the appearance of the metallic coating film is that the brightness decreases and the hue often changes when the angle of observation is increased from a direction substantially perpendicular to the coating surface. Such a color change is represented by "flop" or "tw".
The color seen from the direction almost perpendicular to the painted surface is called "face color",
The color seen at a large angle away from the vertical is "flo
It is called "p color".
The r "contains most of the reflected light from the metallic pigment, while the" flop color "contains almost no reflected light from the metallic pigment.

As a conventional method for coating an object to be coated with a coating film, the above-mentioned solid color or metallic color is used. However, the solid color has no glittering feeling of the metallic color and is a color developed by diffused light. is there.

On the other hand, the metallic color exhibits a variety of glitter and "flop" or "two tone".
It is said that it has a distinctive appearance and is excellent in cosmetics. However, regarding the luster, there is a defect that the metallic particles are too bright.

However, various methods have been proposed in order to improve such defects, that is, to obtain a coating film that is dense and continuous, and has a brilliantly shiny feeling.

For example, the present applicant has also previously proposed a method for forming a coating film using a coating composition containing colored mica or mica coated with barium sulfate (JP-A-3-12478).
No. 0).

[0012] According to this method, a denser, more continuous and astringent shine than a coating film obtained by coating a coating composition containing a pearl mica pigment produced by coating mica with a metal oxide such as titanium dioxide. A coating film having such a glittering feeling can be obtained.

However, since the mica is transparent or translucent, the coloring power and the hiding performance of the colored mica and the barium sulfate-coated mica are inferior, and the color gamut of the coating film that appears appears to be limited.

On the other hand, a material capable of obtaining a clearer interference color is disclosed in, for example, JP-A-59-126468. The coloring power and hiding power of this material are superior to those of the pearl mica pigment coated with the metal oxide such as titanium dioxide, but the brilliance is too strong to give a dense, continuous and astringent shining sensation. Not suitable for obtaining coatings with.

In addition, a pigment obtained by forming a thin film of a transparent metal oxide having a high refractive index such as titanium dioxide on the surface of scaly graphite which is a blackish and opaque material is disclosed in, for example, Japanese Patent Publication No. 3824 and JP-A-52-1
As disclosed in Japanese Patent No. 87422, stable properties are not obtained, and the fact is that they are not manufactured commercially.

[0016]

DISCLOSURE OF THE INVENTION In view of the recent demand for high-quality design finishes in the field of automobile painting, the present invention is a dense, continuous, astringent and bright luster that surpasses the materials mentioned above. It is an object of the present invention to provide a coating composition capable of forming a coating film having a feeling.

[0017]

In view of the present situation, the present inventors have developed a coating composition capable of forming a coating film that maintains a dense, continuous, and astringently shiny glittering feeling for a long period of time. As a result of intensive studies, the graphite flake pigments were prepared by pre-oxidizing the surface of the graphite flake particles and coating titanium dioxide on the surface.Titanium dioxide was evenly and smoothly coated on the surface of the graphite flake, resulting in a bright feeling. The present invention has been completed by finding that it is an excellent pigment exhibiting a stable luster over a long period of time, and that a coating composition using the pigment satisfies the above-mentioned objects and solves the conventional problems.

However, the present invention is a graphite flake in which titanium dioxide is uniformly and densely coated on the surface of graphite flake particles which have been subjected to an oxidation treatment by heating in an oxygen-containing atmosphere and / or an oxidation treatment with a water-soluble oxidizing agent. A coating composition characterized by containing a pigment and at least one layer of the coating composition as a base coat on a substrate, and at least one layer of a transparent top coat on the base coat while the base coat is undried. The present invention relates to a method for forming a multilayer coating film, which comprises simultaneously drying the film.

The present invention will be specifically described below.

The titanium dioxide-coated graphite flake pigment used in the present invention (hereinafter abbreviated as "graphite titanium pigment") is prepared by oxidizing the surface of the graphite flake particles in advance and then hydrating titanium dioxide by a known method. It is obtained by uniformly depositing the substance and baking it at 450 to 950 ° C.

For the oxidation treatment, the graphite flake particles are heated to 200 to 500 ° C. in an oxygen-containing atmosphere, or the graphite flake particles are suspended in water, and then a permanganate such as potassium permanganate or chromium is used. Acid salt,
It is carried out by adding a water-soluble oxidizing agent such as peroxide and stirring at room temperature.

As a production example of the graphite titanium pigment, for example, graphite flake particles are oxidized at 200 to 500 ° C. in an oxygen-containing atmosphere, and the oxidized graphite flake particles are suspended in water, and then further. Oxidation treatment using a water-soluble oxidizing agent is performed, and an aqueous solution of titanium metal salt (eg, titanium trichloride, titanium tetrachloride) and an aqueous solution in which a basic substance is dissolved are simultaneously added to the suspension after the oxidation treatment, It is produced by uniformly and densely depositing titanium dioxide hydrate on the surface of graphite flake particles, and then calcining the obtained pigment at 450 to 950 ° C.

In this case, the titanium dioxide is converted to the rutile type by using a rutile agent such as tin oxide or stannic chloride together with a titanium metal salt. The pigment coated with rutile-type titanium dioxide has excellent weather resistance and is suitable for automobile coatings.

The shape of the above-mentioned graphite titanium pigment has a longitudinal dimension of 1 to 50 μ, and particularly preferably 1 to 1.
A shape having a size of 5 μ and a widthwise dimension of 0.1 to 5 μ, particularly preferably 0.1 to 1 μ is used.
When the dimension in the longitudinal direction is larger than 50 μ, the smoothness is lowered by projecting from the coated surface, and when the dimension in the lateral direction is larger than 5 μ, the brilliance is deteriorated.

The graphite pigment is generally used in combination with other coloring pigments. As the color pigment to be used in combination, an inorganic or organic color pigment to be added as a coloring material to a usual paint can be applied. Preferred color pigments include achromatic color pigments having a particle diameter (diameter) of 1 μm or less, chromatic color pigments, and the like. Specific examples of the achromatic pigment include titanium white and carbon black. As for the chromatic color pigment, the color obtained by mixing titanium white with 1: 1 has Munsell hues of R and Y.
Pigments which are R, Y, YG, G, BG, B, PB, P or RP can be widely used, and among them, pigments having as high transparency as possible are preferable.

The resin component blended in the coating composition of the present invention varies depending on the intended use, but in the general coating field, alkyd resin, polyester resin, epoxy resin,
Examples thereof include polyurethane resin, cellulosic resin, and room temperature dry acrylic resin.

In the field of industrial coatings, especially in the field of automobile coatings, heat-curable resins are generally used. For example, thermosetting acrylic resin / non-aqueous dispersion fine particles (NAD) / melamine resin, thermosetting acrylic resin. / CAB (cellulose acetate butyrate) / melamine resin system, thermosetting polyester (alkyd) resin / melamine resin system, thermosetting polyester (alkyd) resin / CAB or NA
A combination such as D / melamine resin system is used.

In these resin systems, the melamine resin is used as a cross-linking agent, but it is also possible to replace it in whole or in part with polyisocyanate.

The coating composition of the present invention is suitable for the field of automobile coating where a high-quality image finish is desired, and is suitable as a base coat for a two-coat / one-bake finish. The coating composition for automobiles used as this base coat will be described more specifically.

It is preferable that the composition for automobile coating contains the following (a) thermosetting acrylic resin and (b) amino resin as essential components, and if necessary, (c) fine particle dispersion liquid is added thereto. is there.

(A) Thermosetting acrylic resin Methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, methacryl Acid 2
-(Meth) acrylic acid such as ethylhexyl, lauryl acrylate, and lauryl methacrylate and 1 to 22 carbon atoms
Esters with polyhydric alcohols; carboxyl group-containing vinyl monomers such as acrylic acid, methacrylic acid, maleic anhydride; glycidyl acrylate, glycidyl methacrylate; acryloxypropyltrimethoxysilane, methacryloxypropyltriethoxysilane, methacryloxypropyltri-n- Alkoxysilane group-containing vinyl monomers such as butoxysilane; other vinyl monomers such as styrene, vinyltoluene, acrylonitrile, methacrylonitrile, α-methylstyrene and vinyl acetate:
And a compound having one polymerizable unsaturated bond in one molecule and a hydroxyl group-containing vinyl monomer, for example, 2-vidroxyethyl acrylate, 2-hydroxyethyl methacrylate,
Examples thereof include resins obtained by copolymerizing with hydroxypropyl (meth) acrylate.

(B) Amino Resin A partially or completely methylolated amino resin obtained by the reaction of an aldehyde with an amino component such as melamine, urea, benzoguanamine, acetoguanamine, steroganamin, spiroguanamine, dicyandiamide and the like can be mentioned.

(C) Fine Particle Dispersion Liquid (a) The ethylenically unsaturated monomer and / or crosslinkable copolymerizable monomer (for example, ethylene glycol di (meth)).
Acrylic, divinylbenzene, etc.) such as a fine particle dispersion obtained by suspension polymerization or emulsion polymerization in an aqueous medium, or a low SP organic solvent such as an aliphatic hydrocarbon or a high SP organic solvent such as an ester, a ketone or an alcohol. In addition, a fine particle dispersion obtained by copolymerizing an ethylenically unsaturated monomer and / or a crosslinkable copolymerization monomer in a non-aqueous organic solvent in which a monomer is dissolved but a polymer is not dissolved can be mentioned. These fine particle dispersions also include intraparticles crosslinked.

By blending this fine particle dispersion, it is possible to achieve a low viscosity and high solidification of the coating composition with a very small amount of addition, and the coating workability and the orientation of the pigment are remarkably improved, and a cured coating film is obtained. Improves acid resistance and impact resistance.

The mixing ratio of the above-mentioned components (a), (b) and (c) is generally (a) / (b) = 50 to 50 in terms of solid content.
It is in the range of 80/20 to 50, and the component (c) is
It is in the range of 5 to 70% by weight based on the total weight of the components (a), (b) and (c).

The resin component used in the coating composition of the present invention described above is preferably dissolved or dispersed in an organic solvent and / or water in advance. The form includes a solution type, a dispersion type, a high solid type, a non-aqueous dispersion type and the like.

In the coating composition of the present invention, the blending amount of the graphite titanium pigment is preferably 0.5 to 50 parts by weight per 100 parts by weight (solid content) of the resin component, and when it exceeds 50 parts by weight, smoothness is impaired. In some cases, sufficient gloss and sharpness cannot be secured. Also, the amount of color pigment is
Although it depends on the kind of the color pigment used and the like, it is usually about 0.1 to 50 parts by weight per 100 parts by weight (solid content) of the resin component blended in the composition. More specifically, for example, when titanium white is used, the resin component 10
About 0.1 to 10 parts by weight is preferable per 0 part by weight, and
About 1 to 5 parts by weight is particularly preferable. When carbon black is used, it is 0.1 per 100 parts by weight of the resin component.
It is preferably about 5 to 5 parts by weight, particularly preferably about 0.1 to 2 parts by weight. Further, when using a chromatic color pigment, the amount is preferably about 20 parts by weight or less per 100 parts by weight of the resin component,
About 1.0 to 10 parts by weight is particularly preferable.

In the coating composition of the present invention, in addition to the graphite titanium pigment and the coloring pigment, a metallic pigment can be blended if necessary. Examples of such metallic pigments include aluminum powder, bronze powder, stainless powder, titanium powder, chromium powder, pearl mica, colored pearl mica, interference pearl mica, and phthalocyanine plate crystals. The amount of these metallic pigments blended is preferably 30 parts by weight or less, and more preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the resin component solid content.

The method of blending the graphite titanium pigment in producing the coating composition of the present invention is not particularly limited, but typical methods are described in the following (1) to (1).
It shows in (3).

(1) A graphite titanium pigment is added to a resin varnish containing no color pigment or a resin varnish having a color pigment dispersed therein, and the pigment varnish is dispersed in the resin by stirring.

(2) After mixing the resin varnish and the graphite titanium pigment, the mixture is agitated by a dispersing machine such as a ball mill or a sand mill in the same manner as the color pigment.

(3) The graphite titanium pigment is mixed with a solvent, and the mixture is added to the resin after stirring.

In the coating composition of the present invention, if necessary, an additive such as a pigment dispersant, an organically modified silicone and an antifoaming agent,
A curing catalyst and the like can be appropriately added.

The transparent topcoat used in the method for forming a multilayer coating film of the present invention may be any of those prepared by removing the graphite titanium pigment and the coloring pigment from the above-mentioned basecoat.

Next, the method for forming a multilayer coating film of the present invention will be described.

The method of the present invention is characterized in that the above-mentioned coating composition of the present invention is applied and a clear paint is applied to the coated surface.

Examples of the base material (object to be coated) used in the present invention include metals such as steel and aluminum, and polyurethane,
A plastic base material typified by polypropylene or the like can be used. The base material may be electrodeposition-coated and / or pre-coated if necessary.
Alternatively, the undercoat or intermediate coat is applied. The electrodeposition coating method and the undercoating or intermediate coating method are not particularly limited and may be conventionally known methods.

In the present invention, a colored base coat layer is formed on the substrate using the coating composition of the present invention, and a clear paint is applied on the colored base coat layer to form a clear coat layer. The colored base coat layer and the clear coat layer are formed by, for example, appropriately diluting the coating composition of the present invention with a thinner to a viscosity suitable for coating, and then spray-coating the composition onto the substrate, followed by baking or baking. Without doing so, the clear paint for forming the clear coat layer may be spray-coated, and then baking may be performed. Among these methods, the coating composition of the present invention is spray-coated on a substrate, a clear coating for forming a clear coat layer is spray-coated without baking, and then baking is performed. It is preferable to employ the so-called 2-coat 1-bake method. The spray coating method may be electrostatic or non-electrostatic coating. The baking conditions are not different from the conventional ones, for example, at a temperature of 120 to 150 ° C.
The coating film is preferably cured and dried by baking for 40 minutes.

The amount of the coating composition and the clear coating of the present invention to be used is not particularly limited, but the cured dry film thickness of the colored base coat layer is usually about 10 to 30 μm, preferably about 15 to 20 μm, and clear. The cured dry film thickness of the coat layer is usually about 20 to 60 μm, preferably 30 to
It is preferable to use each of the above compositions so as to have a thickness of about 50 μm.

[0050]

The coating film formed by using the coating composition of the present invention shows an interference color due to the high refractive index of the titanium dioxide coating the surface of the graphite titanium pigment by the incident light, and By controlling the film thickness, any color can be made to appear. On the other hand, graphite is essentially a different color system and absorbs a considerable portion of the light that has passed through titanium dioxide, so it is extremely concealable. is there.

Thus, a dense and continuous coating film which is free from finish defects such as color unevenness and which has a unique interference color of "Face Color" and which is brilliantly shiny and excellent in cosmetics can be stably obtained for a long period of time.

This coating film has a three-dimensional and deep feeling as compared with the conventional solid color coating film, and has a dense, continuous, brilliant metallic luster with a glitter feeling suppressed as compared with the metallic coating film. ing. Such metallic luster has not been obtained even with the use of conventional metallic pigments such as aluminum and pearl mica. Furthermore, when a clear coating is applied to the coated surface, sharpness, smoothness, weather resistance, etc. Is further improved.

[0053]

EXAMPLES The present invention will be further clarified with reference to the following examples. In the following, "parts" simply means "parts by weight".

Cationic electrodeposition paint (Electron 94
00, manufactured by Kansai Paint Co., Ltd., and then a polyester / melamine resin-based intermediate coating resin (ES
Primer TP-37, manufactured by Kansai Paint Co., Ltd.) 100
Part, titanium white (R-650, manufactured by Sakai Chemical Industry Co., Ltd.) 20 parts,
Barium Sulfate (Parita # 100, Sakai Chemical Industry Co., Ltd.) 40
Parts and carbon black (Carbon MA-100, Mitsubishi carbon) were mixed in an amount of 4 parts to perform intermediate coating.

On the steel sheet coated with the above electrodeposition coating and intermediate coating, the coating composition of the present invention and the clear coating composition of the present invention having the following compositions were used and the two-coat one-bake method (after coating the coating composition of the present invention,
Subsequently, a clear paint was applied and baked at 140 ° C. for 30 minutes) to form a colored base coat layer having a dry film thickness of 15 to 20 μ and a clear coat layer having a dry film thickness of 30 μ.

The composition of the colored base coat of the present invention used in this coating step is as shown in Table 2 (the composition is parts by weight), and the clear coating was used by removing the pigment component from the composition of the colored base coat. The compositions of the base coats used for comparison are shown in Tables 3 to 5 (the composition is parts by weight).

As the graphite titanium pigment used in the coating composition of the present invention, four types shown in Table 1 below were used.

[0058]

[Table 1] Production Example of Graphite Titanium Pigment 4 pieces of graphite flake particles (PB-85 manufactured by Nishimura Graphite Co., Ltd.) having a particle size of 1 to 100 μm and an average particle size of 36 μm are used.
Heat-oxidize in air at 50 ° C. for 30 minutes. 20 g of the heat-oxidized graphite flake particles are stirred and suspended in 500 ml of ion-exchanged water, 0.2 g of potassium permanganate is added to this suspension aqueous solution, and the mixture is stirred at room temperature for 15 hours to perform the oxidation treatment. After this oxidation treatment, the oxidized graphite flake particles obtained by filtering this suspension are washed with ion-exchanged water to remove the residual potassium permanganate. Next, 250 g of ion-exchanged water was added to 20 g of the oxidized graphite flake particles, and the mixture was stirred to form a suspension, and the temperature was maintained at 75 ° C.
A 0% by weight aqueous hydrochloric acid solution is added to adjust the pH to 1.8. To this suspension, a solution prepared by mixing 13.2 ml of stannous chloride pentahydrate of 53 g / l and 1.86 ml of an aqueous solution of titanium tetrachloride of 407 g / l was added dropwise at a dropping rate of 0.2 ml / min. At the same time, a 5 wt% sodium hydroxide aqueous solution is added dropwise so as to maintain the pH at 1.8. Thus, a mixed oxide hydrate of titanium dioxide hydrate and tin dioxide hydrate is deposited on the surface of the graphite flake particles.

Furthermore, 80 ml of an aqueous solution of titanium tetrachloride of 407 g / l and 80 ml of an aqueous solution of 10% by weight of hydrochloric acid were used.
60 ml of titanium tetrachloride solution was dropped at a dropping rate of 0.2 ml / min, and at the same time, a 5% by weight sodium hydroxide aqueous solution was dropped to maintain the pH at 1.8 to deposit titanium dioxide hydrate. .. After the completion of the dropwise addition of 160 ml of the titanium tetrachloride solution, a 5 wt% sodium hydroxide aqueous solution was added to adjust the pH from 1.8 to 6.0, the solid substance was filtered off, and washed with ion-exchanged water. Drying at 15 ° C. for 15 hours gives a gold interference titanium dioxide hydrate coated graphite flake pigment with excellent color development. When this was further calcined in air at 520 ° C. for 30 minutes, a rutile type titanium dioxide-coated graphite flake pigment of gold interference, which was more excellent in color developability, was obtained.

Graphite titanium pigment BLUE, PUR
PLE and GREEN are obtained in a similar manner by varying the amount of titanium tetrachloride used and the amount of titanium dioxide coated as described above.

[0061]

[Table 2] In Table 2, (1) to (8) are as follows.

(1) Sicotrans Red L2
715D: manufactured by BASF, trade name: transparent iron oxide (2) cyanine green G5301: manufactured by Dainichi Seika, trade name (3) cyanine green G314: manufactured by Sanyo Pigment Co., Ltd.
Product name (4) Hostaperm Pink EB tran
s: manufactured by Hoechst, trade name Quinacridone Red (5) Black Pearls BP-1300:
Product name Carbon Black manufactured by Cabot Corporation (6) 15% styrene, 15 methyl methacrylate
%, Butyl methacrylate 40%, 2-ethylhexyl acrylate 13%, hydroxyethyl methacrylate 15% and acrylic acid 2% were copolymerized in xylol using the polymerization initiator asobisisobutyronitrile. Acrylic resin solution having a content of 50%, a solution acid value of 80 and a solution viscosity of Y (Gardner, 25 ° C.).

(7) Mitsui Toatsu product, trade name U-Van 28
SE (8) Kansai Paint Co., Ltd., core-crosslinked non-aqueous dispersion (based on JP-A-3-126770)

[0064]

[Table 3]

[0065]

[Table 4]

[0066]

[Table 5] The contents of the pigments used in Tables 3 to 5 are as follows.

Perylene Red R-6436: Bayer Perylene Pigment Yellow-YT915D: Ciba Geigy Quinacridone Pigment White R-701: Teika Titanium Dioxide Pigment Carbon Black BP-1300: Cabot
Carbon black pigment Yellow 3R: Yellow pigment made by Ciba-Geigy Oxide yellow XLO: Yellow iron oxide pigment made by Titanium Industry Co., Ltd. Brominated phthalocyanine green 2YK: Phthalocyanine pigment made by Dainippon Ink and Chemicals Infinite color: Low-order titanium oxide coating made by Shiseido Mica White Pearl: Titanium dioxide coated mica manufactured by Merck Co., Ltd. The paints of Examples 1 to 8 and Comparative Examples 1 to 24 which are made into paints based on the formulations shown in Tables 2 to 5 are applied, and clear paints are applied thereon. A two-coat / one-bake coating was applied to a gonio-spectrophotometer GC manufactured by Murakami Color Research Laboratory Co., Ltd.
Incident angle 45 ° under the condition of C light source and 2 ° field of view by MS-4
Table 6 below shows the results of color measurement at fixed 5 ° intervals of 5 ° from -30 ° to 20 °.

From these results, Examples 1 to 8 and Comparative Examples 9 to
In No. 24, the Munsell value changes due to the change of the light receiving angle, which is a "face color" peculiar to metallic coatings.
It can be seen that the solid colors of Comparative Examples 1 to 8 show a small change in the Munsell value due to the change in the light-receiving angle, while the changes in the "flop color" are shown.

[0069]

[Table 6] Regarding the glittering feeling, which is the other feature of the metallic coating film, the laser type metallic feeling measuring device ALCOPE LMR-100 manufactured by Kansai Paint Co., Ltd. was improved, and the luminous flux was set to φ50μ, and the condition of -45 ° incidence / 35 ° light reception was used. The measurement surface was scanned at a distance of 8 mm, and 255 points were measured to measure the average value [IV (AVE)] and standard deviation [IV (PET)] of the brightness (IV value). The results are shown in Table 7.

From these results, Examples 1 to 8 are Comparative Examples 9 to 2.
It can be seen that [IV (PET)] showing a change in the intensity of shine is smaller than that of No. 4, and that it has a dense, continuous and astringent shining feeling.

[0071]

[Table 7] In addition, regarding the long-term retention of the glittering feeling that is particularly required for automobile paints, data on the bakuro test results in the outdoors, such as Florida, have not yet been obtained, but Atlas Co., Ltd. Table 8 shows the results of the accelerated weathering test for 3,000 hours using a Canon Weatherometer Ci65 manufactured by K.K.

From these results, a pigment obtained by coating the surface of mica, which has already been used in automobile paint, with titanium dioxide,
Even when compared with a coating composition containing a so-called pearl mica pigment, long-term retention is not inferior.

[0073]

[Table 8]

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Claims (5)

[Claims] 1. A graphite flake pigment in which titanium dioxide is uniformly and densely coated on the surface of graphite flake particles which are subjected to an oxidation treatment by heating in an oxygen-containing atmosphere and / or an oxidation treatment with a water-soluble oxidizing agent. A coating composition comprising: 2. The coating composition according to claim 1, wherein the titanium dioxide-coated graphite flake pigment is a pigment coated with rutile titanium dioxide. 3. The titanium dioxide-coated graphite flake pigment has a longitudinal dimension of 1 to 50 μm, a lateral dimension of 0.1 to 5 μm, and a blending amount of 0.5 to 50.
The coating composition according to claim 1, which is in weight%. 4. The coating composition according to claim 1, which is a thermosetting acrylic resin-based base coat. 5. A base coat is coated with at least one layer of the coating composition of claim 1 as a base coat, and while the base coat is undried, at least one layer of a transparent top coat is coated thereon, and both coatings are dried at the same time. A method for forming a multilayer coating film, which comprises: